1. Field of the Invention
This invention relates to a shearing machine mounted on a tip of an arm of a working machine, such as a power shovel, for shearing various kinds of steel material. 2. Statement of the Prior Art
When dismantling or destroying reinforcing bars, buildings of a reinforced concrete construction, scraps of steel, articles or chemical machinery of steel alloy, a steel material shearing machine is usually used, the machine being attached to one end of an arm of a working machine, such as a power shovel. An example of such shearing machines is disclosed in U.S. Pat. No. 4,519,135 and shown in FIG. 8. The shearing machine disclosed in the Patent includes a lower stationary jaw 2 integrally attached to one end of an arm 1 of a power shovel. An upper movable jaw 3 is connected to the lower stationary jaw via a support shaft 4 so that it may be opened and closed vertically in a scissors-like manner. The upper movable jaw 3 may be opened and closed by means of a plurality of hydraulic cylinders 5 mounted on the arm 1. In this manner, the movable jaw 3 is moved relative to the lower stationary jaw so as to shear or cut a steel material clamped therebetween. The lower stationary jaw 2 and upper movable jaw cooperate, in their engaged position, to define a central concave area, so as to prevent a steel material clamped therebetween from slipping off in a forward direction.
The opposite surface of the lower stationary jaw 2 and upper movable jaw 3 cooperate to form a recess 8 defined by side plates 6, 6 and a forward-end connection plate 7. Pressure plates 9 and 10 are disposed at a forward end of a recess 8 in the lower stationary jaw 2 and at a forward end of the upper movable jaw 3, respectively. In this manner, the pressure plate 10 on the upper movable jaw 3, when actuated, is inserted into the recess 8 in the lower stationary jaw 2 and abuts with the pressure plate 9, so as to prevent the upper movable jaw 3 from moving sideways away from the lower stationary jaw. The lower stationary jaw 2 and upper movable jaw 3 include attached thereto a plurality of lower shearing blades 11 and upper shearing blades 12 adapted to be inter-engaged relative to one another.
Another example of such a shearing machine is disclosed in Japanese Patent Publication [KOKOKU] No. 56-49273. Although not shown in the drawings, a shearing machine disclosed in this Publication includes a cylinder case detachably mounted on one end of an arm of a power shovel by means of a rotatable device, and a pair of cutters. Each cutter includes a shearing blade pivotably mounted on a support shaft extending transversely in the cylinder case.
The shearing machine disclosed in the above United States Patent is constructed so that the upper movable jaw 3 may be inserted into the recess 8 formed in the lower stationary jaw 2. Further, each of the upper and lower jaws includes attached thereto a pressure plate 10, 9. This causes such a shearing machine to be relatively large in size, complicated in construction, and significantly heavy in weight, thus making manufacturing cost thereof relatively high. In addition, such a shearing machine requires a relatively large-sized power shovel.
On the other hand, the shearing machine disclosed in the above Japanese Publication is relatively small in size and lightweight. It should be noted, however, that, in such a shearing machine, the cutter body tends to move sideways away from a steel material upon shearing thereof in a direction perpendicular to open close direction of the cutter. Thus, such a shearing machine becomes incapable of securely shearing or cutting a steel material over time of use.